Questions & Answers about Не переходи улицу здесь!
Why does this sentence use the imperfective verb переходи instead of the perfective перейди?
When telling someone not to do something (a negative prohibition), Russian almost always uses the imperfective aspect. Even though crossing the street is a single, complete action, the negative word не triggers the imperfective переходи. If you were telling them to cross, you would use the perfective: Перейди улицу!
Why is it улицу instead of the dictionary form улица?
Улица (street) is the direct object of the verb—it is the thing being crossed. Because of this, it needs to be in the accusative case. For feminine nouns ending in -а, the ending changes to -у.
How would I say this to a stranger or a group of people?
The ending -и in переходи tells us this is the informal, singular "you" (ты form), used for a friend or child. To warn a stranger or multiple people, you need the formal/plural form by adding -те: Не переходите улицу здесь!
Do I need a preposition like "across" in Russian?
No preposition is needed here! The verb переходить directly takes the accusative case object (улицу). The prefix пере- built into the verb already carries the meaning of moving "across" from one side to the other.